Added support for get parameters in service definitions

Hey,
In my current project i have a lot of services defined in one wsdl file using all the same endpoint url. 
The specific services are defined as a parameter in the endpoint url.
Example: 
  'http://localhost:8050/SOAP?service=Foo' for the service 'Foo',
  'http://localhost:8050/SOAP?service=Bar' for the 'Bar' service

I had the problem that the node-soap module only checks for the endpoints path address, with the result that the first service is used and the method is not found. To fix this i added an additional check for the url query checking if the query parameter from the definition exists and is the same as the one from the called endpoint. Additional arguments are ignored. 

The fix works fine for me, hope that i didn't missed something anywhere?